The present invention relates to a method of encapsulating a topical composition in a breakable capsule.
The intended field of application is particularly but not exclusively that of pads containing cream type cosmetic compositions.
Powder puffs have been used for a long time in cosmetics to deposit and spread face powder over the face. They are generally received in the lid of the box containing the powder, and powder is taken from the box by pressing the puff against the supply of powder.
The need has also been felt to spread liquid or semiliquid substances on the face, in particular creams for taking care of the skin, and requiring pads of a different kind, and in particular pads that are disposable. That makes it necessary to have available, independently, both the cream for spreading in a receptacle and the disposable pad for putting the cream onto the skin and for spreading it, and in some circumstances that does not present any difficulty.
In other circumstances, that are more occasional, particularly when testing samples, or when making an application in an unusual place, a pad has been devised in which the substance for spreading is adjacent to the applicator in a small container that is easy to open and that contains sufficient substance for one application.
Such single-use pads are difficult to manufacture automatically, and in particular it is difficult to make the capsule that forms the small container.
An object of the present invention is to provide a method of producing capsules containing the composition for spreading, which capsules are easy to open.
Another object of the present invention is to propose applying the capsule production method to making single-use pads containing the composition for spreading.
These objects are achieved by a method of encapsulating a topical composition in a breakable capsule constituted by at least a first deformable film that is impermeable to said composition, the method comprising the following steps: a first step in which at least a portion of said first film is deformed elastically so as to constitute at least one blister; a second step in which said topical composition is injected into said blister; a third step in which a second film that is impermeable to said composition is applied onto said first film so as to close said blister; and a fourth step in which said second film and said first film are sealed together around the periphery of said blister, said portion of said first film being suitable for shrinking after release of said capsule so as to cause the pressure inside the capsule to be greater than atmospheric pressure; and while said capsule is being made, at least one weak region is made at least in said blister, thus making the capsule suitable for being broken by exerting pressure on said capsule.
The sequence of steps in making the capsule enable an automatic method to be applied to producing a capsule whose mechanical properties are well adapted to the problem of opening said capsule, with opening being performed merely by applying pressure between two fingers, while production costs are kept down to an acceptable level.
It will be understood that the method consists in a first step in making a cavity in an elastically deformable film which would normally be plane, with the topical composition for spreading on the skin then being introduced into the cavity.
The cavity is held in shape during the steps of filling, applying the second film, and sealing. Thus, when the capsule is released, the first film retains substantially the shape it has been given since the hermetically closed capsule contains said composition. However, given the elasticity of the film, on being released, i.e. when the capsule is released, it applies pressure on said composition. Thus, the pressure which acts on the composition is equal to atmospheric pressure plus the pressure induced by the elasticity of the film.
The system for opening the capsule is provided by local weakening of the film that constitutes the blister. Thus, pressure exerted on the capsule increases internal pressure, causing said capsule to be pierced in its weak region, thereby releasing the topical composition. It will be understood that the pressure to be exerted on said capsule becomes all the more effective in releasing the composition contained therein with increasing pressure inside the capsule as induced by the film.
According to another feature of the method, said portion of the first film constituting said blister is subjected to deformation that is both plastic and elastic such that said first film shrinks in part after said capsule has been released, whereby the pressure inside the capsule is not less than atmospheric pressure.
It is not easy to obtain deformation that is purely elastic leading to optimum pressure inside the capsule, and as a general rule the deformation obtained is accompanied by structural modification to the film giving rise to a fraction of deformation that is irreversible, i.e. so-called xe2x80x9cplasticxe2x80x9d deformation. Under such circumstances, the pressure inside the capsule is clearly smaller.
In a preferred implementation of the invention, when the two films are assembled together around the outline of said blister, the sealing includes a fraction of reduced width to constitute a weak region.
Thus, when the capsule is squeezed, opening takes place through the weak region of the sealing, at the interface between the two films.
Advantageously, a fraction of said portion of said first film constituting the blister is transformed locally so as to constitute a weak region.
The particular feature of this implementation lies in the fact that the capsule is opened through a face of said first film, and not via its interface with the second film. In this configuration, it is possible to eject the topical composition from the center of the capsule and not necessarily from the peripheral seal of said capsule.
Finally, in order to weaken the film locally, it is possible to flatten the film or to deform it, or else to melt the film locally by means of a heater or an ultrasound device.
In another preferred implementation, suction is established between a portion of the deformable first film and a recess so as to apply said film portion against the inside wall of said recess so as to constitute said blister.
It will be understood that the fact of placing the film over a cavity constituting a recess and of establishing suction between said film and said cavity tends to press the film against the inside wall of said cavity. Naturally, this wall has orifices enabling air to be sucked out.
In another preferred implementation, said first film and said second film are sealed together by means of an ultrasound device.
This implementation presents the advantage of melting only those portions of the film that are in contact, and of not including any heat source that might damage the capsule or its content.
Advantageously, the encapsulation method of the invention is applied to making pads. For this purpose, at least a first sheet of foam is applied and secured to the outside wall of said first film in order to constitute the pads.
A layer of foam is applied to the capsule made in accordance with the invention for the purpose of spreading said composition on the skin. The foam is secured to the capsule via the edges of the two films that are sealed together.
In order to make both faces of the pad agreeable to the touch, it is preferable to apply a second sheet of foam and/or of textile material on the outer wall of said second film.
In order to protect at least the face that includes the applicator foam, a protective film constituting a membrane is advantageously applied to said first sheet of foam.